Ngakoue said on Monday that it happened after a running play in the Jaguars' 10-3 AFC wild-card victory at EverBank Field, but he could not recall whether Incognito used the N-word.
"No, I don't remember, but, you know, he said what he said," Ngakoue said. "He knows what he said. I don't gotta repeat it."
Ngakoue, whose father is a native of Cameroon and whose mother is from the West Indies, said Incognito insulted his ethnicity.
"I've been playing this game since I was a little kid. You hear all types of stuff," Ngakoue said. "Stuff's not going to bother you, but somebody says something about your ethnicity, that's really kind of taking it a little bit too far.
"I'm all with trash talk. It's part of the game, but you can't say certain things."
Ngakoue said on Twitter on Sunday night that a Bills player wearing No. 64 was going to "have to come harder than some weak racist slurs." Ngakoue ended his tweet with the hashtag #Iaintjonathanmartin!. Incognito wears No. 64.?
Incognito was not available during the Bills' open locker room period on Monday, but two teammates spoke in his defense and told reporters they did not hear him use any racial slurs.
"I was next to Richie the entire game and Richie did not say one thing, and if he did, [you] best believe I would've been one of the first people to basically check him on it because there's races, there's a lot of stuff that's going on in this country and there's boundaries," said offensive tackle Dion Dawkins. "But if he did overstep, I would have said something. As far as I know, he did his thing."
Said center Eric Wood, via 13WHAM ABC and Fox Rochester sports anchor Toby Motyka on Twitter: "It was chippy out there but I didn't hear anything. I know Dion tweeted something that he didn't hear it and Richie's done a lot in the past few years to restore his image and I hope it's not all thrown away off of speculation and whatever. But honestly I didn't hear it, so I can't speak either way on it."
Jaguars defensive end Calais Campbell and defensive tackle Abry Jones said they did not hear Incognito use any racial slurs, but Campbell said Ngakoue told him what Incognito allegedly said. Campbell also said it seemed like Bills players were deliberately trying to antagonize Jaguars players.
"I think they were really trying to get us to lose our cool and try to get penalties," Campbell said. "There were a lot of guys talking as if it was coached to get us to lose our cool, so we can get a 15-yard penalty. I think that's something we're going to have to deal with because we've shown we can be a little too aggressive at times.
"[Racial slurs are] going too far, though. I understand trying to give yourself an advantage and you see somebody trying to egg them on to try to get a penalty, I understand that. But there's boundaries. You don't go to racial slurs; that's not OK."
Jones said he could tell Ngakoue was upset but wasn't sure why.
"I didn't hear anything but I know how Yan is," Jones said. "For him to go to social media and to put it out there, I don't think he's lying. That's pretty big for Yan. I know Yan, he usually don't tweet. He usually swings, so that's an improvement."
Incognito, 34, has made the Pro Bowl each of his three seasons since signing with the Bills in 2015. Buffalo gave Incognito a second chance in the NFL after the Miami Dolphins suspended him for the final eight games of the 2013 season for his role in a bullying scandal in which former NFL offensive lineman Jonathan Martin was a target.
NFL investigator Ted Wells released a report in 2014 detailing "a pattern of harassment" against Martin by Incognito and other Dolphins players that included racial slurs. Incognito's attorney later called the report "replete with errors."
The NFL cleared Incognito later in 2014 to return to football, but he spent that season out of the league before joining Buffalo the next year.
ESPN's Mike Rodak contributed to this report.